Multiparticulates of uniform dimensions with modified drug release properties can readily be manufactured by melt extrusion technology. Melt extrusion is a solvent-free single-step process for manufacturing multiparticulates and is particularly useful for drug release modification. By selection of suitable polymers and additives, melt extrusion technology can be used both to enhance the solubility, and subsequently the bioavailability, of poorly water soluble drugs as well as to retard drug release of moderate to highly water soluble drugs for controlled release products.
The backbone of melt extrusion technology is the application of thermoplastic materials which act as binders for embedded drugs in solution or dispersion form within the matrix. Thermoplastic polymers with low glass transition temperatures (Tg) are preferred for processing by melt extrusion. Lower processing temperatures are also preferred with respect to the stability of heat sensitive drugs and other necessary excipients. Polymer glass transition temperatures can also be further reduced to facilitate processing at lower temperature with optional addition of plasticisers.
WO 9614058 provides a sustained-release pharmaceutical formulation, comprising a melt-extruded blend of a therapeutically active agent, one or more materials selected from the group consisting of alkylcelluloses, acrylic and methacrylic acid polymers and copolymers, shellac, zein, hydrogenated castor oil, hydrogenated vegetable oil, and mixtures thereof; and one or more hydrophobic fusible carriers which provide a further retardant effect and are selected from the group consisting of natural or synthetic waxes, fatty acids, fatty alcohols, and mixtures thereof, the fusible carrier having a melting point from 30 to 200° C. The melt-extruded blend is divided into a unit dose containing an effective amount of said therapeutically active agent to render a desired therapeutic effect and providing a sustained-release of said therapeutically active agent for a time period of from about 8 to about 24 hours.
Furthermore, WO 9614058 describes a method of preparing a sustained-release pharmaceutical extrudate suitable for oral administration. The method comprises:
blending a therapeutically active agent together with (1) a material selected from the group consisting of alkylcelluloses, acrylic and methacrylic acid polymers and copolymers, shellac, zein, hydrogenated castor oil, hydrogenated vegetable oil, and mixtures thereof and (2) a fusible carrier selected from the group consisting of natural or synthetic waxes, fatty acids, fatty alcohols, and mixtures thereof; said retardant material having a melting point between 30-200° C. and being included in an amount sufficient to further slow the release of the therapeutically active agent;
heating said blend to a temperature sufficient to soften the mixture sufficiently to extrude the same;
extruding said heated mixture as a strand having a diameter of from 0.1-3 mm;
cooling said strand; and
dividing said strand to form non-spheroidal multi-particulates of said extrudate having a length from 0.1-5 mm; and
dividing said non-spheroidal multi-particulates into unit doses containing an effective amount of said therapeutically active agent, said unit dose providing a sustained-release of said therapeutically active agent for a time period of from about 8 to about 24 hours.
Thus, in practice, the stranded extrudate is congealed on a conveyor belt and cut into pellets. Such pellets typically have a cylindrical shape.